1. Field of the Invention
The present invention relates generally to filtration apparatus for removing particulates from a liquid or gas stream, and it relates more particularly to a new and improved mounting arrangement for a tube-type filter element used in such apparatus.
2. Description of the Prior Art
Filtration apparatus having tube-type filter elements are found in a variety of industrial and commercial applications wherein purification of liquids or gas streams is being performed. Typically, such apparatus includes a vertically mounted tank having a lower inlet port and an upper outlet port with one or more generally elongate filter tubes mounted therebetween and suspended within the tank from a tube sheet. The filter tubes are constructed of a porous material, such as ceramic and extend through apertures formed in the tube sheet arranged in spaced relation one to another. The filter tubes have closed ends and fluid entering the inlet port of the filter tank must pass through the walls of the filter tubes to reach the outlet port of the filter. Solids suspended within the liquid or gas stream are thereby deposited on the walls of the filter tubes and thus are removed from the fluid or gas stream.
With continued use of the filtration apparatus, solid matter accumulates on the walls of the filter tubes to such a degree that a filter cake is formed and cleaning or replacement of the filter tubes is necessitated. To effect such replacement, it is known to construct the filter tubes such that they each have an integral annular flange at their upper ends with a gasket disposed between the lip of the flange and the upper surface of the tube sheet. A bolt and washer arrangement can then be used to secure the flange to the tube sheet when the filter tube is properly positioned within its respective tube sheet aperture.
A disadvantage of the foregoing arrangement for mounting the filter tubes is that a bolt and washer arrangement renders it difficult to maintain the filter tube in sealed relation to the tube sheet over the broad range of temperatures to which the filtration apparatus is subjected. In this regard, the effects of differential expansion as between the tube sheet and filter tube materials, respectively, can cause leakage to occur at the gasket between the tube sheet and filter tube. In addition, since the filter tube is typically constructed of a brittle ceramic material, a bolt and washer arrangement can cause fracturing of the filter tube flange if installation of the filter tube is not performed with care.
In co-pending application, Ser. No. 827,738, filed Feb. 10, 1986, assigned to the assignee of the present invention, filter apparatus is disclosed wherein a filter tube is provided with a cylindrical hub having a diameter greater than the diameter of the body portion of the tube. The juncture of the hub and body portion defines an annular surface which is cooperable with an annular surface provided in the aperture of the tube sheet to form an interface between the tube sheet and filter element. An annular gasket is interposed between the surfaces of the tube sheet aperture and the filter tubes. A plurality of removable pins extend through the tube sheet and into each of the hubs to secure the hubs of the filter tubes in place. While such an arrangement prevents damage to the filter tubes and ensures a proper seal between the filter tube and tube sheet, it would be desirable to further simplify the construction of the filter tube and tube sheet mounting configuration whereby the filter tubes are effectively sealed to the tube sheet over a wide range of temperatures and are also removable with greater convenience.